Saw this in a local Tescos, not sure if you can use it for the iphone as well?http://www.energizer.com/products/energi-to-go/ipod-charger/Pages/ipod-battery-charger.aspx
Lightweight and portable fuel for your iPod, Nano and Mini
Energizer® Energi To Go® Portable Power for iPod is a battery-powered charger that provides extended play time to a variety of iPod models. Sleek enough to complement the iconic styling of the iPod, the compact charger is lightweight and travels easily.
Comes complete with:
* One reusable Energizer® Energi To Go® Charger
* Licensed Apple iPod connector
* Two Energizer® Ultimate Lithium AA batteries